I'd think you'd need a firewall. I recently started passing all of a friend's email through my IMail/SpamAssassin server on the way to his Exchange server. One of the accounts had an auto-forward to a Blackberry, and Spam on a device like that is a real pain.
So, I defined a "bogus" domain locally (friendsdomain.local), and set up my IMail (with all FriendsDomain accounts mirrored) to forward non-spam to <sameusername>@friendsdomain.local. MX changes were: mail.friendsdomain.com A (For OWA to Exchange). mx 5 mail.friendsdomain.com (For inbound, local-recipient from the 'net) became: mail.friendsdomain.com A (So they can still OWA to Exchange) unchanged. mx 5 mail.myIMailDomain.net (Imail) mx 10 mail.FriendsDomain.com (In case I'm down - Not as likely as Exchange being down<g>) That didn't work. The Spam reduced about 10%. So, I removed the "failover" MX record. That didn't work. The Spam reduced about another 10%. So, I blocked port 25 from getting to Exchange unless from my IMail box. Bingo. Yes, you are right! The Spammers don't follow the rules! You need to allow port 80 to mail.YourDomain.tld from the world and dissallow port 25 unless local or mx.YourDomain.tld. This can probably be done with some sort of add-on port-diddling software but it's trivial with a firewall. I encourage other listizens to contribute the names of such these add-ons, as I bit-the-bullet and put up a firewall recently (about the time I lit a wireless network for 100's of strangers<g>). Dan Barker -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of T. Bradley Dean Sent: Thursday, December 02, 2004 4:29 PM To: [EMAIL PROTECTED] Subject: RE: [IMail Forum] Great MX firewall to put in front of your imail server Another question... Currently my DNS is setup like this: IN MX 10 mail mail IN A 1.2.3.4 With 1.2.3.4 being my public IP address. So mail.Domain.com is my mx and the hostname my users use for IMAP4, SMTP, and POP3. If I start using an MX firewall I'll have to change to something like this: IN MX 10 mx mx IN A 1.2.3.2 mail IN A 1.2.3.4 All domains will use the same mx with the same IP (1.2.3.2), but, like you said before, the Baracuda will then forward to different IPs for mail.Domain1.com, mail.Domain2.com, mail.Domain3.com, etc. Users will still use mail.Domain.com for SMTP / POP3 access to iMail. Assuming all the above is correct, what's to keep spammers from mailing to my old mx of mail.Domain.com (1.2.3.4)? It would bypass the mx firewall and go into iMail directly. How common is this? If they port scan they are going to get a hit, I have to keep outside SMTP access to iMail for my users. Do I have this setup wrong? Thanks, ~Brad -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Grant Griffith - IMail Sent: Tuesday, November 30, 2004 10:40 AM To: [EMAIL PROTECTED] Subject: RE: [IMail Forum] Great MX firewall to put in front of your imail server No reason to do that. All you have to do is make you MX point to the barracuda, just like IMGate. Then the Barracuda allows you to tell it where to send the email for that domain after it processes the email. So you MX will point to the Barracuda for all domains and then when you setup the Barracuda to accept email to that domain, you tell it to send mail to the corresponding domain. Thanks, Grant Griffith EI8HT LEGS, A Division of ETC (877)483-3393 (812)933-5390 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of T. Bradley Dean Sent: Tuesday, November 30, 2004 1:28 PM To: [EMAIL PROTECTED] Subject: RE: [IMail Forum] Great MX firewall to put in front of your imail server I'm looking at the Barracuda too, although not the $13k version! I'm also considering going with IMGate. But let me ask a question about how it would be setup? Currently I have multiple domains like this: 65.116.252.100 Domain1.com 65.116.252.101 Domain2.com 65.116.252.102 Domain3.com Barracuda only accepts one IP address. And of course, these IPs are already attached to my network firewall. If I setup an MX firewall are all of my domains going to become virtual domains on a single IP in iMail? ~Brad -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jeff Cox Sent: Tuesday, November 30, 2004 8:13 AM To: [EMAIL PROTECTED] Subject: [IMail Forum] Great MX firewall to put in front of your imail server We use imail and declude and transact 400,000 messages per day over about 250 domains. The fact is that neither declude imail combo, nor imail internal antispam and antivirus could keep up with our traffic, even though we had dual xeon's and a new high performance dell server. With our junk mail traffic doubling every 3 months as a small ISP with only about 3K customers we were going to have to buy and deploy multiple imail servers that would have been expensive in hardware and software. This got me to thinking I would have to switch mail server software to sendmail that is more efficient as well as can more easily be spilt up across severs based on process (pop, smtp, imap, etc) rather than by accounts. Then I found something that let me keep my investment in my current mail server. For about $13K we bought a barracuda 600 spam fire wall (http://www.barracudanetworks.com/). The features are amazing, it can cluster easily, and the updates are fairly cheap. You still need imail and /or declude for internal mail protection and outbound mail (and unless you want to buy an outbound unit from barracuda as well). But this product has saved me from switching mail servers. You can apply for a free 30 day demo! =Jeffery Cox Chief Operating Officer McMinnville Access Company DBA OnlineMac / Centricata www.onlinemac.com www.centricata.com [EMAIL PROTECTED] --- [This E-mail Scanned for viruses by Onlinemac.com] To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
